Curved metal tubes or rods have been bended by secondly carrying out a bending process after firstly extruding of straight tubes or rods by the extrusion process. However, it is difficult to get precious and standard curved products, because the curved tube or rod has been caused to have the ununiform section due to deformation during bending the tube or rod. Especially, it is very difficult to manufacture the bended tube having longitudinal fins on an inner surface or an outer surface of the tube as shown in FIG. 8, by using the conventional extruding device, because the conventional extruding device causes the bended tube to have a thin or thick wall at some portion thereof, to have a distorted section, and to be wrinkled and folded on the outer surface thereof.